OAKLAND -- Law enforcement leaders say they fear that to balance the budget, California lawmakers will weaken a powerful crime prevention tool: preschool.

"I strongly urge all of our policymakers to protect the funding we have for early education," Alameda County District Attorney Nancy O'Malley said at a Tuesday news conference. "The investment that we make in children today will save millions of dollars tomorrow in incarceration costs."

Gov. Jerry Brown's budget proposal includes a cut to state preschool programs of $180 million, or 23 percent. The plan would leave 17,000 children without access to a state-subsidized preschool; it also would slash per-pupil funding by 10 percent, which could diminish the quality of the program.

Brown also is proposing to repeal the law requiring school districts to offer a two-year kindergarten program for some children, starting this fall.

Fight Crime: Invest in Kids California, an association of police chiefs, district attorneys and survivors of violent crimes, promoted the importance of such programs at the news conference, held at Oakland's Greenleaf Elementary School. State preschools lost 17,000 slots and $70 million in the last budget cycle. Further cuts, the association said, would have lasting societal consequences.

Oakland police Chief Howard Jordan said that for every $1 invested in quality early education programs, taxpayers will see a return of $10 or more.

A 2005 study provides some evidence for such a claim. For decades, researchers with the Perry Preschool Study followed a group of 123 low-income African Americans from Ypsilanti, Mich., who were 3 or 4 years old in the 1960s. Some children were randomly assigned to the same high-quality preschool program, and the others weren't.

When tested at age 5, those in the preschool group were more than twice as likely to have IQs of 90 or higher (67 percent vs. 28 percent) than those who didn't. By age 14, they were more than three times as likely to have reached a basic achievement level. They were less likely to be placed in special education programs, more likely to graduate from high school and, as adults, to be employed. They were also less likely to be arrested for violent crimes.

The study's cost-benefit analysis found that for every dollar invested in the preschool program, $16 was returned -- $12.90 of it to the public, mostly from crime saving and increased taxes as result of higher earnings.

Greenleaf Elementary School, in an Oakland neighborhood plagued with violent crime, is piloting transitional kindergarten this year. The statewide program was designed for the 125,000 children who will miss the kindergarten cutoff date when it rolls from Dec. 2 to Sept. 1.

Whether it remains a state law, school districts in Oakland, Antioch, Castro Valley, Livermore, Martinez, Palo Alto and San Jose plan to offer the new grade-level in the fall.

O'Malley said many consider public safety to be a question of protecting society from criminals.

"It's important to protect the community," she said. "On the other hand, what we lose is that there are ways to prevent crime."

Read Katy Murphy's Oakland schools blog at www.IBAbuzz.com/education. Follow her at Twitter.com/katymurphy.